diff --git a/x/registry/server.go b/x/registry/server.go
index 0acddbca..69eae4be 100644
--- a/x/registry/server.go
+++ b/x/registry/server.go
@@ -29,11 +29,7 @@ const (
 
 type Server struct {
 	UploadChunkSize int64 // default is DefaultUploadChunkSize
-	minioClient     *minio.Client
-}
-
-func New(mc *minio.Client) *Server {
-	return &Server{minioClient: mc}
+	S3Client        *minio.Client
 }
 
 func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -84,7 +80,7 @@ func (s *Server) handlePush(w http.ResponseWriter, r *http.Request) error {
 		return err
 	}
 
-	mcc := &minio.Core{Client: s.mc()}
+	mcc := &minio.Core{Client: s.s3()}
 	// TODO(bmizerany): complete uploads before stats for any with ETag
 
 	type completeParts struct {
@@ -136,7 +132,7 @@ func (s *Server) handlePush(w http.ResponseWriter, r *http.Request) error {
 		if err != nil {
 			var e minio.ErrorResponse
 			if errors.As(err, &e) && e.Code == "NoSuchUpload" {
-				return oweb.Invalid("uploadId", uploadID, "unknown uploadId")
+				return oweb.Invalid("uploadId", uploadID, "")
 			}
 			return err
 		}
@@ -158,7 +154,7 @@ func (s *Server) handlePush(w http.ResponseWriter, r *http.Request) error {
 			key := path.Join("blobs", l.Digest)
 			if l.Size < minimumMultipartSize {
 				// single part upload
-				signedURL, err := s.mc().PresignedPutObject(r.Context(), bucketTODO, key, 15*time.Minute)
+				signedURL, err := s.s3().PresignedPutObject(r.Context(), bucketTODO, key, 15*time.Minute)
 				if err != nil {
 					return err
 				}
@@ -175,7 +171,7 @@ func (s *Server) handlePush(w http.ResponseWriter, r *http.Request) error {
 				for partNumber, c := range upload.Chunks(l.Size, s.uploadChunkSize()) {
 					const timeToStartUpload = 15 * time.Minute
 
-					signedURL, err := s.mc().Presign(r.Context(), "PUT", bucketTODO, key, timeToStartUpload, url.Values{
+					signedURL, err := s.s3().Presign(r.Context(), "PUT", bucketTODO, key, timeToStartUpload, url.Values{
 						"uploadId":   []string{uploadID},
 						"partNumber": []string{strconv.Itoa(partNumber)},
 					})
@@ -198,7 +194,7 @@ func (s *Server) handlePush(w http.ResponseWriter, r *http.Request) error {
 		// Commit the manifest
 		body := bytes.NewReader(pr.Manifest)
 		path := path.Join("manifests", path.Join(mp.Parts()...))
-		_, err := s.mc().PutObject(r.Context(), bucketTODO, path, body, int64(len(pr.Manifest)), minio.PutObjectOptions{})
+		_, err := s.s3().PutObject(r.Context(), bucketTODO, path, body, int64(len(pr.Manifest)), minio.PutObjectOptions{})
 		if err != nil {
 			return err
 		}
@@ -215,7 +211,7 @@ func (s *Server) handlePull(w http.ResponseWriter, r *http.Request) error {
 func (s *Server) statObject(ctx context.Context, digest string) (pushed bool, err error) {
 	// HEAD the object
 	path := path.Join("blobs", digest)
-	_, err = s.mc().StatObject(ctx, "test", path, minio.StatObjectOptions{})
+	_, err = s.s3().StatObject(ctx, "test", path, minio.StatObjectOptions{})
 	if err != nil {
 		if isNoSuchKey(err) {
 			err = nil
@@ -230,16 +226,16 @@ func isNoSuchKey(err error) bool {
 	return errors.As(err, &e) && e.Code == "NoSuchKey"
 }
 
-func (s *Server) mc() *minio.Client {
-	if s.minioClient != nil {
-		return s.minioClient
+func (s *Server) s3() *minio.Client {
+	if s.S3Client != nil {
+		return s.S3Client
 	}
-	mc, err := minio.New("localhost:9000", &minio.Options{
+	s3, err := minio.New("localhost:9000", &minio.Options{
 		Creds:  credentials.NewStaticV4("minioadmin", "minioadmin", ""),
 		Secure: false,
 	})
 	if err != nil {
 		panic(err)
 	}
-	return mc
+	return s3
 }
diff --git a/x/registry/server_test.go b/x/registry/server_test.go
index ef878c64..114eab79 100644
--- a/x/registry/server_test.go
+++ b/x/registry/server_test.go
@@ -87,7 +87,7 @@ func TestPushBasic(t *testing.T) {
 	}`)
 
 	hs := httptest.NewServer(&Server{
-		minioClient:     mc,
+		S3Client:        mc,
 		UploadChunkSize: 5 * MB,
 	})
 	t.Cleanup(hs.Close)